Python Inversion-of-Control framework

Synopsis

The ioc module provides a framework to dynamically inject dependencies in Python applications. This intends to reduce coupling between application and infrastructure, and application and third-party libraries.

Usage

Basic

In it's most basic usage, dependencies can be declared and invoked using a few simple calls to functions in the ioc library.

>>> import ioc
>>>
>>> req = ioc.require('MY_REQUIREMENT')
>>> ioc.provide('MY_REQUIREMENT', 'foo')
>>> print(req)
'foo'

The procedure is simple: state your requirement by a symbolic name and call to ioc.require(), and then provide the requirement using ioc.provide().

When an application fails to provide a dependency for a requirement, an exception is raised upon invocation:

>>> import ioc
>>>
>>> req = ioc.require('MY_REQUIREMENT')
>>> print(req)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "requirement.py", line 11, in inner
    self._setup()
  File "ioc/requirement.py", line 58, in _setup
    self._injected = self._provider.resolve(self._names[0])
  File "ioc/provider.py", line 33, in resolve
    raise UnsatisfiedDependency(name)
ioc.exc.UnsatisfiedDependency: MY_REQUIREMENT

Class properties

A call to ioc.require() will not return the actual dependency (it might not be resolved yet) but a wrapper that mimics the behavior of the (to-be) injected dependency.

>>> import ioc
>>>
>>> repr(ioc.require('not_resolved'))
'<ioc.requirement.DeclaredRequirement object at 0x101db7ac8>'

This might not always be a desirable property, for example with Python C-extensions that enforce datatypes on their input parameters. To solve this problem, the ioc module provides the ioc.class_property() decorator. This adds a descriptor to a class that will always return the dependency as it was injected.

>>> import ioc
>>>
>>> class Foo:
...     bar = ioc.class_property('bar')
...
>>>
>>> ioc.provide('bar', 'baz')
>>>
>>> repr(Foo.bar)
'<property object at 0x101ce5ae8>'
>>>
>>> foo = Foo()
>>> repr(foo.bar)
"'baz'"

Advanced usage

Changelog

1.3

Append symbol dependencies to an existing iterable.
Load literal dependencies from environment variables.
Fix parser loading literal dependencies as symbols.
Allow default arguments in signatures with ArgumentDependencyInjector.
marshmallow 3.0.0b11 compatibility.

1.2

Add support for copy.copy() and copy.deepcopy().
Allow default argument with ioc.class_property().
Make ioc.class_property() a real class property.
Allow overriding dependencies at runtime.

Metadata

Release files for python-ioc 1.13.0

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Source distribution for python-ioc 1.13.0
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